Tissue former including a yankee drier having raised surface portions

ABSTRACT

A METHOD AND MECHANISM FOR FORMING HIGH BULK LOW DENSITY WEB MATERIAL FORM A STOCK SLURRY FEEDING THE STOCK ONTO A TRAVELLING FOURDRINIER WIRE TO FORM A WEB AND TRANSFERRING THE RELATIVELY WET WEB ONTO THE SURFACE OF A HEATED YANKEE DRYER HAVING A PATTERNED RAISED SURFACE THEREON AND PRESSING UNCOMPPRESSED FORMED WEB ONTO THE SUFACE SO THAT THE PORTION OF THE WEB ARE COMPRESSED AGAINST THE RAISED PORTIONS OF THE SURFACE WITH INTERMEDIATE PORTIONS UNCOMPRESSED AND COMPLETING SUBSTANTIALLY THE ENTIRE REMAINING DRYING PROCESS THERMALLY WITH THE WEB BEING CARRIED ON THE SURFACE IN A FIXED POSITION AGAINST THE RAISED AND NONRAISED AREAS FOR THE ENTIRE REMAINING DRYING PROCESS ON THE YANKEE DRUM.

April 23, 1974 A, E Y 3,806,406

TISSUE FORMER INCLUDING A YANKEE DRIERHAVING RAISED SURFACE PORTIONS Filed Dec. 20, 1971 United States Patent O 3,806,406 TISSUE FORMER INCLUDING A YANKEE DRIER HAVING RAISED SURFACE PORTIONS Donald A. Ely, Roscoe, Ill., assignor to Beloit Corporation, Beloit, Wis. Filed Dec. 20, 1971, Ser. No. 209,943 Int. Cl. D21f 5/02 US. Cl. 162206 Claims ABSTRACT OF THE DISCLOSURE A method and mechanism for forming high bulk low density web material from a stock slurry feeding the stock onto a traveling fourdrinier wire to form a web and transferring the relatively wet web onto the surface of a heated Yankee dryer having a patterned raised surface thereon and pressing uncompressed formed web onto the surface so that portions of the web are compressed against the raised portions of the surface with intermediate portions uncompressed and completing substantially the entire remaining drying process thermally with the web being carried on the surface in a fixed position against the raised and nonraised areas for the entire remaining drying process on the Yankee drum.

BACKGROUND OF THE INVENTION The invention relates to a method and structure for the production of low density web material such as a paper toweling or the like and generally relates to the provision of a mechanism for producing bulky paper sheet for use in tissue, toweling, sanitary products and like web material. This type of material embodies a highly desirable combination of softness, bulk and high absorbency characteristics.

In high bulk sheet material of the type to which the present invention is related, the sheets are formed of fibers of Wood pulp or synthetic material and are arranged to form a web with a repeated pattern wherein the fibers are compressed and between the compressed areas are uncompacted or uncompressed .fibers. The compressed areas lend to the strengh and appearance of the paper while the uncompressed areas contribute to its softness and thickness or bulk and particularly contribute to high absorbency characteristics useful for household and commercial sheet material.

In the conventional manufacture of paper webs, the web is formed on a traveling forming surface such as a fourdrinier wire and water is expressed from the web in a pressing operation which flattens and compacts the fibers. Subsequent thermal drying is effected from the compressed web and the resultant sheet is flat and compact.

Efforts to produce a high bulk noncompact high absorbent web have embodied the formation of a web with patterned imprints on a web with the areas of the imprints being compressed and the areas between the imprints being uncompressed. One process for forming such a sheet has embodied removing the Web from the fourdrinier after formation and pressing the web against a knuckled traveling wire, partly thermally drying the web on the wire and then depositing the web from the wire onto a smooth thermal drying drum.

In accordance with the principles of the present invention, disadvantages of the aforedescribed method and other previous methods are avoided in that the preformed loose uncompressed web is pressed onto the patterned surface of a Yankee dryer drum and maintained supported on the patterned surface throughout its entire drying process. This avoids the additional unnecessary handling of the uncompressed web which is done in methods heretofore available and avoids the flattening which occurs in thermal drying of the sheet on a flat dryer drum surface. By transferring the formed uncompressed web directly from the fourdrinier to the surface of a Yankee dryer wherein the surface is specially formed to provide a patterned support for the web, the web is pressed against the patterned support surface on the Yankee dryer and the web is supported with the fibers thereafter being undisturbed on the Yankee throughout the thermal drying process during which the web is dryed from its condition as it is received from the fourdrinier to a substantially bone dry condition. The drying process with the escape of steam through the fibers provides a better formed more bulky more strong web because the fibers permit the free escape of steam and maintain in their preformed interrlated positions during the entire thermal drying process, with the web essentially supported on the raised patterned support areas of the Yankee.

A further advantage of the present arrangement over methods heretofore available for forming high bulk tissue resides in a more eflicient drying procedure in that there is a more intimate contact between the thermal drying surface and the web during the drying process. In previous processes which did not employ the imprinting technique, the Web was delivered to a smooth surface Yankee dryer drum and removed from the drum by a creping doctor so that the resultant product was relatively compact and the web was relatively thin compared with webs formed by processes which form an imprint on the surface of the web leaving the areas between the imprints relatively loose and uncompact. However, in the processes which imprint the web so that it has a pattern of small compact areas with the areas in between remaining uncompact, there is poor surface to web contact on thermal dying drums. Furthermore, the carrying and handling of the web after the imprinting which requires bending it around curved surfaces disturbs the fiber formation making a less strong sheet. Further, after the imprinted web is transferred to a thermal surface, the imprinted areas lack surface-to-surface contact with the thermal dryer drum reducing the rate of heat transfer. Also, since the web is supported on the thermal surface only over a portion of its area, it tends to flatten while being dryed thereby reducing its bulkiness and tending to encourage the fibers to sag together and as a consequesce, the looseness and flufliness and overall absorbency of the finished product is reduced.

It has been found that by the use of the process of the instant invention, the procedure suflices to produce the desirable combination of softness, bulk and absorbency characteristics heretofore sought, and also results in a high bulk, high porosity paper sheet possessing substantially the same tensile strength as that of conventional paper of the same basis weight in creped form even though tensile strength has not been developed by overall pressing. It has also been found that paper sheets formed in accordance with the present invention are especially adapted for use in paper toweling, sanitary tissues, facial tissues and like products where the softness, bulk, absorbency and tensile strength characteristics are desirable and of value.

Accordingly, it is a general object of the invention to provide an improved method and mechanism for forming a paper sheet having improved qualities of bulk, softness and absorbency for a given basis weight. A further object of the invention is to provide a unique process for the manufacture of high bulk tissue and toweling weight papers having increased thickness or caliber in relation to the Web weight while not yielding sheet strength.

A still further object of the invention is to provide an improved structure and process for the manufacture of high bulk Webbing wherein the process attains a higher efficiency than those heretofore available and attain a more rapid, more eificient heat transfer in the thermal drying process thereby enabling higher manufacturing speeds and mechanisms of reduced size.

A still further objective is the provision of an apparatus and method for forming loose flulfy paper sheet material having high strength and having high absorbency characteristics by the improved retention of distributed fiber formation and the reduction of disturbance of such fiber formation during the drying process.

The drawings and description will disclose preferred embodiments of the invention, and it will be apparent to those skilled in the art that alternative equivalent structures and processes may be employed Within the principles of the teachings of the invention as set forth in the specification, claims and drawings in which:

DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat schematic elevational view of a paper making machine constructed and operating in accordance with the principles of the present invention;

FIG. 2 is a detailed fragmentary view of the surface of a dryer drum constructed in accordance with the present invention;

FIG. 3 is a fragmentary plan view of a portion of a dryer drum surface as also shown in FIG. 2; and

FIG. 4 is a somewhat schematic sectional view taken through a web of paper formed in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a paper web W is first formed in its partially dewatered uncompressed state on a traveling dewatering surface such as a fourdrinier wire 10. The wire is supported on a breast roll 11 and travels along a dewatering path in the direction indicated by the arrowed line to a couch roll 12. The stock slurry is deposited on the traveling forming wire from a headbox 15 having a slice opening. Dewatering occurs along the traveling run with the wire passing over dewatering foils 13 and suction boxes 14.

While the invention contemplates the formation of toweling and like material from wood fiber stock, the use of artificial fibers in whole or in part are also contemplated, and the webbing can be formed of stock including polyamid fibers, vinyl fibers, acrylic fibers and polyester fibers sold under the respective trademarks of Nylon, Saran, Orlon and Dacron, all suitable for the construction of the sheet material.

The web which will be formed on the fourdrinier will be relatively noncompact and will be removed from the wire after the couch 12 by a pickup and transfer felt 16 carried on a pickup roll 17 which may have a suction gland therein to effect transfer of the web onto the felt. The felt carries the web directly to apply it to the surface of a Yankee dryer drum 19. The web is carried onto the dryer drum with the felt passing over a pressing roll 20 which forms a pressure nip to lay the web onto the outer surface of the drum 19. In some instances, minor predrying can occur by through dryer 18 which directs a flow of hot air through the web, but the amount of drying which occurs at this location is relatively small and in a preferred arrangement, this predrying may be omitted.

Similarly, in one form, drying is not completed on the Yankee dryer drum 19 and a small amount of subsequent drying can be accomplished by an after-dryer shown at 27, but in the preferred arrangement the entire thermal drying will occur on the Yankee dryer. The predryer 18 and postdryer 27 are provided only in certain circumstances where additional drying capacity is required.

A significant feature of the invention is that the relatively loose uncompact formed web is carried directly from the fourdrinier to the surface of the Yankee dryer 19 and pressed thereon by the rolls 20. The roll 20 may be a steel roll or a rubber covered roll and apply sufiicient pressure to press the felt to press the web onto the dryer surface to impress the patterned imprint into the web.

That is, the surface of the Yankee dryer is specially constructed to have a raised patterned imprinting surface thereon with a plurality of raised, relatively uniformly spaced mounds or peaks 21 on'the surface, as shown in FIGS. 2 and 3. Between these mounds or peaks are recessed areas 22. When the web is pressed onto the patterned raised surface, the portions of the web opposite the peaks will be compressed as shown at 23 in FIG. 4. The portions of the web between the peaks will remain relatively uncompressed and fill the valleys or depressions between the peaks. Slight indentations will, of course, occur between the peaks inasmuch as the web will be pressed slightly by the resilient felt in the nip N. However, the still uncompressed web as it enters the nip N will be pressed into intimate surface-to-surface contact with the entire outer area of the dryer drum. Since the Yankee dryer drum is heated, evaporation of the moisture within the drum is greatly increased over that of a smooth surfaced Yankee inasmuch as the entire surface area must be measured including the side slopes and peaks of the raised areas thereby increasing the area of contact between the web and the surface of the Yankee.

Further, as the thermal evaporation of the moisture occurs and the steam flows out through the fibers of the web, it will escape readily through the fibers and as drying occurs, the fibers will remain in the relative positions and are not disturbed by flexing or movement of the Web such as occurs where it is carried on a knuckled wire. The fibers remain in their relative interlaced positions throughout the entire drying process while the web is being carried around the suface of the Yankee dryer. When the web is removed, it is carried off of the Yankee dryer by a felt 25 passing over a transfer roll 26.

To aid in keeping the dryer drum clean of loose fibers a brush 28 may extend across the entire length of the Yankee dryer drum to brush out any fibers which may adhere to the drum. This brush may be rotated at a desired speed and moved against the drum with the pressure needed to clean the drum and a vacuum removal systern may also be employed to carry away the loose fibers.

The entire drum surface may be chrome plated for smoothness and increasing the heat transfer and to increase its hardness and wearing capabilities. It also may be case hardened for prolongation of wear. Various manufacturing procedures may be used to form the raised imprint on the drum surface and a knurling or embossing procedure may be employed using a deep knurling tool which provides the desired raised imprint during the drum manufacture and the surface may thereafter be hardened or chrome plated as desired. The raised portions may take any pattern desired and may be a uniform pattern of raised areas or a patterned arrangement to provide the appearance necessary in the resultant dryed web.

. As the web is removed, it has a loose flutfy consistency and relatively high tensile strength suitable for toweling or other materials dependent upon the type of pulp, basis weight and other factors in the initial formation of the web.

I claim as my invention:

1. The method forming a soft bulky sheet from a fiber stock slurry comprising the steps of depositing the slurry on a traveling forming surface and removing water therefrom to form a partially dewatered bulky web, pressing the web on the surface of a heated Yankee dryer drum from the drum surface with the alternately compressed and uncompressed areas of the web forming a bulky sheet.

2. The method of forming a soft bulky sheet from a fiber stock slurry in accordance with the steps of claim 1 and including partially drying the web prior to laying it on the Yankee dryer drum.

3. The method of forming a soft bulky sheet from a fiber stock slurry in accordance with the steps of claim 1 including additionally drying the web after it is removed from the Yankee dryer drum.

4. A mechanism for forming a soft bulky sheet from a fiber stock slurry comprising in combination,

means depositing the slurry on a traveling forming surface and removing water therefrom to form a partially dewatered bulky web, means transferring the partially dewatered web from the forming surface to a heated Yankee dryer drum at a transfer location,

said Yankee dryer having a surface with a multitude of distributed small raised mounds, said transferring means including a felt and presson roll carrying the felt and forming a press-on nip with the Yankee at said transfer location pressing the web on the surface of the Yankee with the web being unsupported on its outer surface following said press-on nip, said mounds compressing the web at the points of engagement with the web portion between the mounds remaining relatively uncompressed and accommodating the release of water from the web with the fibers being rearranged as the web is pressed over the mounds, and means removing the dryed web from the drum with the alternately compressed and uncompressed areas of the web forming a bulky sheet.

5. A mechanism for forming a soft bulky sheet from a fiber stock slurry constructed in accordance with claim 4 wherein the mounds on said Yankee dryer drum surface are formed by knurling the surface.

6. A mechanism for forming a soft bulky sheet from a fiber stock slurry constructed in accordance with claim 4 wherein said drum surface is chrome plated.

7. A mechanism for forming a soft bulky sheet from a fiber stock slurry constructed in accordance with claim 4 wherein the outer surface of said Yankee dryer is case hardened.

8. A mechanism for forming a soft bulky sheet from a fiber stock slurry constructed in accordance with claim 4 and including auxiliary drying means in advance of the dryer drum to reduce the moisture consistency of the web to a predetermined dryness before pressing it on the Yankee dryer.

9. A mechanism for forming a soft bulky sheet from a fiber stock slurry constructed in accordance with claim 4 including auxiliary drying means after the drum to dry the web to bone dryness after it leaves the drum.

10. A mechanism for forming a soft bulky sheet from a fiber stock slurry constructed in accordance with claim 4 including a cleaning brush in engagement with the drum surface positioned on the nonweb supporting location of the drum between the press-on and take-off locations.

References Cited UNITED STATES PATENTS 3,537,954 11/1970 Justus 162305 988,247 3/ 1911 Criswell 162-109 1,548,783 8/1925 Lorenz 162113 2,826,827 3/1958 Metz 34110 X 3,301,746 1/ 1967 Sanford et al. 162l13 3,337,388 8/1967 Wosaba 162109 FOREIGN PATENTS 323,621 12/ 1928 Great Britain 34-110 OTHER REFERENCES A.B.I.P.C., vol. 36, No. 12 (June 1966), p. 1739, abtract 8726, Erving, Chrome Dryer Surfaces.

Calkin: Modern Pulp and Paper Making, 3rd ed., Reinhold Publishing Corporation, -l957, pp. 373 and 374.

'S. LEON BASHORE, Primary Examiner R. V. FISHER, Assistant Examiner US. Cl. X.R. 

